Going to chofu, should i book a hotel?

Hi, i'll be visiting Japan in May.
Im going to Tokyo Rocks a 2 day festival at Ajinoto Stadium, in the Chofu area. theres a chance i might miss the last train (not sure what time is the last train to shinjuku/shibuya).

Im not sure wether i should just book a hotel in chofu for 2 nights during the festival or are there any other options thats practical. I would prefer to stay around Shibuya and just stay there for the festival, but not sure if its possible with the train hours and all.

Any help is much appreciated

I don't know how big the event is. But if it's a big event, I guess public transportation to Tokyo central should be available. Otherwise, a number of people coming to the event have no way to get back home.